#21  
Old 05-17-2020, 02:07 PM
Murf Murf is offline
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Originally Posted by 2nd67GTO View Post
Exactly! Thinking of ditching the shroud and strapping the fans directly to the radiator leaving the rest of the core to free flow while cruising. The more I look at things the less hope I have for getting a properly placed fan into a shroud.



Marshal


I’m no expert but I would be willing to bet that it would run cooler with a mechanical fan & no shroud at all. I noticed no real change when I put the shroud on my wife’s 65. YMMV of course.

Murf


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  #22  
Old 05-28-2020, 03:31 PM
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2nd67GTO 2nd67GTO is offline
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To pick back up after a couple weeks moving stuff, buying and selling a house I’m back on it.

Took the pulley cover off water pump and clutch bolted right in. Ended up using the 2797 severe duty, the 2747 low profile was too short. Installed Derale 17119 fan. I did end up having to remove the AC pulley cover to clear the fan, but the fan clears the rest by at least 1/2”.

I had to remove radiator to get the clutch over the WP studs. I imagine the clutch will be within 3/8” from core but should clear. I’m not concerned with the motor moving and having the clutch spank the radiator. With solid motor mounts, if the motor moves, I got bigger problems than a banged up radiator. I haven’t put the rad back in yet. Too hot in the garage now. Can’t keep the sweat outta my eyes.
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  #23  
Old 05-28-2020, 04:49 PM
Murf Murf is offline
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Originally Posted by 2nd67GTO View Post
To pick back up after a couple weeks moving stuff, buying and selling a house I’m back on it.



Took the pulley cover off water pump and clutch bolted right in. Ended up using the 2797 severe duty, the 2747 low profile was too short. Installed Derale 17119 fan. I did end up having to remove the AC pulley cover to clear the fan, but the fan clears the rest by at least 1/2”.



I had to remove radiator to get the clutch over the WP studs. I imagine the clutch will be within 3/8” from core but should clear. I’m not concerned with the motor moving and having the clutch spank the radiator. With solid motor mounts, if the motor moves, I got bigger problems than a banged up radiator. I haven’t put the rad back in yet. Too hot in the garage now. Can’t keep the sweat outta my eyes.


Lookin good! I’d be surprised if it don’t cool it off.

Murf


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  #24  
Old 05-28-2020, 06:07 PM
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Originally Posted by Murf View Post
I’m no expert but I would be willing to bet that it would run cooler with a mechanical fan & no shroud at all. I noticed no real change when I put the shroud on my wife’s 65. YMMV of course.

Murf
Without the shroud, the fan has no ability to pull air through the radiator, so you're basically rendering the fan useless by doing that. Not necessarily an issue if you spend very little time in traffic, but if you do, it's going to overheat.

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  #25  
Old 05-28-2020, 06:50 PM
Murf Murf is offline
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Originally Posted by ZeGermanHam View Post
Without the shroud, the fan has no ability to pull air through the radiator, so you're basically rendering the fan useless by doing that. Not necessarily an issue if you spend very little time in traffic, but if you do, it's going to overheat.


Alrighty them.


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  #26  
Old 05-31-2020, 03:53 AM
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Way back in 1967 when my GTO was only two weeks old I went down to the Pontiac dealer and purchased a fan shroud because the engine was getting warm sitting in traffic. My H.O. without A/C didn't come with a fan shroud. The results from adding a shroud wasn't totally expected, but actually makes sense. Idle and low speed operation dropped 15° with the shroud, but made freeway running 5° warmer. So not having a shroud will help on the higher speed cruising.

I've pretty well proven to myself that there is a high pressure area under the engine of our A bodies at freeway speeds to a point where the SD 2797 is on more than buzzing around town at 40 MPH or so. What I always wanted to do, but have been too lazy to try it, was to install an air dam to divert airflow and create a low pressure zone under the engine to pull air through the radiator. I would not put it up front by the bumper simply because it would be dead ugly. I was thinking using a stiff aluminum sheet starting flat from the radiator support to just before the cross member where it would make a sharp bend down to slightly below the cross member. Much of the air starting to go under the front of the car would be deflected from under the engine.

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  #27  
Old 06-01-2020, 03:28 PM
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2nd67GTO 2nd67GTO is offline
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Well, success. Sort of. Sitting in the garage idling ambient mid 70s, she’ll get to 165. Driving at 70+ on highway at 3000 rpm she crept to 184. Again ambient low to mid 70s. 160 stat.

Shroud should be here later this week. I have a sneaky suspicion that with the addition of the shroud I’ll be fine. Just have to wait and see. May not get shroud on for awhile. Moving 700 miles North. Taking truckload up Wednesday this week, then RV and GTO the following week. Will be at RV park till July 9th when escrow closes. Only allowed 1 extra vehicle. Gotta keep Mama’s Toyota out. If mama ain’t happy.... Car will be in storage till then.

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  #28  
Old 06-01-2020, 03:30 PM
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2nd67GTO 2nd67GTO is offline
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If she holds at 180 or there abouts with shroud, I’ll bump up to a 180 thermostat.

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  #29  
Old 06-01-2020, 04:01 PM
Murf Murf is offline
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Originally Posted by 2nd67GTO View Post
If she holds at 180 or there abouts with shroud, I’ll bump up to a 180 thermostat.


Glad to hear you are having some success. I do believe that 180 is being more than cautious.
Water doesn’t boil till 212 and that’s with no pressure. If I remember correctly the sending units for idiot lights in 70’s Pontiacs were set to go on at around 240.
Before anyone has a cow, I’m not suggesting running at 240.
I had a 455 68 Firebird that ran around 220 most of the time. It never gave me any problem.
The wife’s car hasn’t gotten past 190 yet with the all radiator. I don’t think of that as hot at all.
Keep us posted on how you do with the shroud on.

Good luck!
Murf


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  #30  
Old 06-04-2020, 04:18 PM
Joe's Garage Joe's Garage is offline
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Quote:
Originally Posted by ZeGermanHam View Post
Without the shroud, the fan has no ability to pull air through the radiator, so you're basically rendering the fan useless by doing that. Not necessarily an issue if you spend very little time in traffic, but if you do, it's going to overheat.
The air has to come from someplace. While some may be pulled from behind the radiator and pushed back over the engine, it would never be as much volume as even a normal 4-blade fan would pull. The fan creates a low-pressure spot between it and the radiator and the air is pulled thru the radiator to that lower pressure and then thru the fan and over the engine.

At cruising speed or above, the air flow is much higher due to the forward movement of the radiator, but the fan still creates that low-pressure area, which assists the air flow thru the radiator.

That's why the older (pre-1970) pickup trucks usually only had a heavy duty fan and no shroud. It was all you needed.

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